1. Field of the Invention
The present invention relates generally to electrical analysis of light images using charges transfer in a semiconductor. It relates more particularly to a two dimensional photosensitive device, and to a device for analyzing images using this photosensitive device.
2. Description of the Prior Art
Solid state devices are known in the prior art for the analysis of light images, which are intended to be used in television cameras for delivering an electrical video signal. They are characterized both in the arrangement of the photosensitive zone, and also the reading system and the removal of the charges created by the image. It is also well-known to use such charge transfer devices for carrying out these various operations as described. For example, in the work of SEQUIN and THOMPSETT: "Charge Transfer Device" New York (1975) (pages 152 to 169):
in the systems known as "raster transfer" or "interline structure", in which the light beams are received on charge transfer registers; in such device the charge transfer is achieved over large areas, thus constituting a drawback due to the fact that it is currently difficult to obtain high yields for the production of such large areas; PA0 in charge injection devices called "CID", that do not present this drawback, but generally require a reinjection of the charges in the semiconductor substrate and have various drawbacks, e.g. noise and difficulties for defining the value of the necessary capacitances during and after the reading of the charges. PA0 a matrix with N lines.times.M photosensitive zones or points, the image to be read being projected on said matrix and converted into electrical charges; PA0 a memory with M points, called "line memory", adapted for successively receiving the signal charges accumulated for each line; PA0 a register such as a charged coupled device receiving parallel-wise the content of the line memory and emitting series-wise the electrical signal of image analysis. PA0 a plurality of photosensitive elementary zones, arranged on the same semiconductor substrate on N lines and M columns, said zones being insulated from each other, in said zones electrical charges being created depending upon the received light, each of the elementary zones comprising a MOS capacitance, forming a first zone for collecting the charges, comprising a single grid common to all capacitances of the same line, and a second zone for collecting the charges, electrically coupled to the capacitance; PA0 connecting and controlling means, delivering parallel-wise the electrical charges created in the M photosensitive zones of the same line, and this successively for the N lines, said means comprising a plurality of reading diodes, arranged in columns between the elementary photosensitive zones, in order that each receives succesively on order the charges of at least two elementary zones, belonging to two different lines; PA0 means forming a charge screen, arranged between each photosensitive zone and the connecting means, said screen means presenting a plurality of grids, brought to a constant voltage, and arranged in columns between reading diodes and the photosensitive zones.
More generally, and in addition to the problems cited above, there is the the question of the compatibility of, both the time required for light integration and, also the time required for the charge transfer. For example, in the case of television screen scanning time, which is, according to the 625 lines standard, approximately 52 .mu.s per line presentation and 12 .mu.s per line return time.